Evaluation of Sesame (Sesamum indicum) for Optimum Nitrogen Requirement Under Usual Farmers’ Practice of Basal Organic Manuring in the Savanna Ecoregion of Nigeria

Nitrogen is a great determinant of crop growth and consequently farmers’ crop yield. Hence, its roles become indispensable and cannot be substituted in crop and animal productions. Unfortunately, its availability, volatilization, leaching losses, toxic nitrate pollution etc. become a serious tropical problem, as being aggravated by improper soil management practices and incorrect nitrogen applications. However, obtaining a reliable information regarding the most suitable dosage of nitrogen required to supplement the pre-existing ‘ploughed-in’ or ‘buried-in’ organic residues (as commonly practiced by farmers), for optimum performance of sesame in the study area is reasonable. Such information is crucial, particularly in the areas of proper recommendation of nitrogen fertilizer, for efficient crop production as well as promotion of environment-friendliness in the use of chemical fertilizers. Greenhouse experiment was conducted to determine the response of sesame to eight levels (0, 20, 40, 60, 80, 100, 120 and 140 kg N ha-1) of urea application. The trial was arranged in completely randomized design (CRD), replicated nine times. All the treatments were equally fortified with basal application of decaying plant residues found on the farmland, at two weeks before sesame propagation. Data collected on growth and yield parameters were analyzed using ANOVA at p< 0.05. Basal application of the pre-existing plant residues alone cannot successfully and sustainably enhance sesame performance in the study area. Growth significantly increased with increasing dosage of urea application till 80 kg N ha-1. Moreso, uptake of nitrogen (N) did not significantly (p < 0.05) increase with increasing application rate of nitrogen particularly at > 80 kg N ha-1 . Application of 80 kg N ha-1 resulted in optimum growth and yield parameters of sesame. Application of 80 kg N ha-1 significantly (p < 0.05) enhanced uptake of most nutrients and produced the highest oil contents. Nitrogen application > 80 kg N ha-1 significantly enhanced uptakes of micronutrients particularly manganese and zinc. There was a significant decline in the percentage of oil content produced as the levels urea application were above 80 kg N ha-1. Application of 80 kg N ha-1 is therefore adequate and recommended for improved performance of sesame and soil quality in the area investigated. Keywords: Sesame, Nitrogen, Organic manure, Savanna ecoregion, Yield, Nutrient uptak